Note: Descriptions are shown in the official language in which they were submitted.
'77~59
Description
Clamp Assembly
Technical Field
This invention relates generally to a clamp
assembly for controllably gripping an article and more
particularly to such a clamp assembly having a pair of
pressurizable gripping members.
Background Art
In the material handling industry, increased
use is being made of automated handling equipment. In
particular, robots are increasingly being used to
transfer articles and to load and unload articles from
machine tools. If all of the workpieces being handled
are identical, a clamp assembly for holding the article
during transfer can be easily designed. However, if a
diversity of articles having varying sizes and shapes
is pxesented to the handling device, the clamp
asssembly for holding the articles generally becomes
more complex. Often sensing and control devices are
required to adapt a clamp assembly to variously sized
and shaped articles. Additionally, if the articles
being handled are partially finished, care must be
taken to prevent damage to previously finished surfaces
or features of the article. This problem has,
heretofore, resulted in adding to the complexity of the
clamping or gripping assembly.
One approach to control]ably gripping an
article susceptible to damage is disclosed in U.S.
Patent 3,915,311 issued to Glen A. Ball, et al, on
October 25, 1975. In the Ball patent, a pressurizable
inflatable bladder is mounted inside a ring for J
circumferentially gripping a large circular object such
as a tire core. A somewhat similar device is also
77~35~
--2--
disclosed in U.S. Patent 2,756,883 issued to Irvin F. Schreck
on July 31, 1956. However, both of the above clamping devices
are effective for clamping only a predetermined, specifically-
sized article.
The present invention provides a simple, effective device
for controllably gripping variously sized and shaped articles and
is directed to overcoming one or more of the problems as set forth
above.
Summary of The Invention
In accordance with one aspect of the present invention,
there is provided a clamp assembly for controllably gripping an
article, comprising: a pair of opposed frame members each includ-
ing a rigid wall portion and a support arm, each of said support
arms having a first end attached respectively to one of said rigid
wall portions and a second end spaced from said first end, said
support arms being pivotally interconnected at a point intermediate
said first and second ends and sald frame members being pivotally
movable about said point between a first position at which the
frame members are spaced apart and a second position at which the
frame members are adjacently disposed with respect to one another;
means for pivotally moving said frame membel-s between said first
and second positions; a pair of pressurizable gripping members,
each having a compliant article-contacting surface and being
respectively attached to said frame members; and means for con-
trollably pressurizing at least one o said gripping members.
A preferred embodiment of the invention is a clamp assem-
bly for controllably gripping an object, comprising: a first
frame member; a second frame member; a irst gripping member
, . ~
'
7~3S~
-2a-
attached to said first frame member; a second gripping member
attached to said second frame member; first means for moving at
least one of said first frame member and said second frame member
between a first position at which said first and second gripping
members are spaced apart and a second position at which said
first and second gripping members axe in substantially abutting
relationship; a pair of support arms each having a first end
attached to a respective one of said first and second members,
and a second end attached to said first means, said support arms
being pivotally interconnected at a point intermediate said first
and second ends and being pivotally movable about said point
between a first position at which the frame members are spaced
apart and a second position at which the frame members are
,~ adjacently disposed with respect to one another; and second
means for pressurizing at least one of said first and second
gripping members in response to said first and second gripping
members being at said second position.
Clamp assemblies for use with automated material handling
devices generally require a sensor or other data input to adapt the
assembly to a configuration conducive for controllably gripping a
randomly-presented article of indeterminate size or shape. The
present invention simply and effectively solves this problem by
providing plural pressurizable gripping members having compliant
article-contacting surfaces. The gripping members are controllably
pressurized to form the compliant surface at least partially about
the article and apply a minimal, predetermined contact force on
the article. The force applied is sufficient for safely lifting
or moving the article, but is not of a magnitude to render damage
~1~7~
-2b-
to vulnerable features of the article. In addition, rigid
non--compliant gripping surfaces are avoided, thereby eliminating
: any risk of marring or otherwise damaging previously finished
surfaces on the article.
;~
:
.'
..
'~.
'7~S9
Brief Description Of The Drawings
Fig. 1 is an isometric view of an embodiment
of the present invention with opposed members of the
clamp assembly spacecd apart.
Fig. 2 is an isometric view of an embodiment
of the present invention with the opposed members
adjacently disposed.
;:~ Fig. 3 is an isometric view of an embodiment
' of the present invention showing an article gripped
-` lO between the opposed members being placed in a machine
tool.
Fig. 4 is to top plan view of an embodiment of
the present invention with sections broken away to show
' details of the frame members.
: 15 Fig. 5 is a sectional view of the present
invention, taken along the line V-V of Fig. 4.
,~
sest Mode For Carrying Out The Invention
-~ The preferred embodiment of a clamp assembly
for controllably gripping an article 10 is generally
indicated by the reference numeral 12. The clamp
assembly 12 includes a first frame member 14 and a
second frame member 16 opposedly mounted with respect
to the first frame member. As best shown in Figs. 4
and 5, each of the frame members have a
,~ semi-cylindrical rigid wall portion 18,20, a
reinforcing brace 21,22 attached to the radially inner
surface of the wall portions 18,20, a flange 23,24
extending about the periphery of the wall portions
18,20, and a pair of support arms 26,28. Each of the
support arms include spaced upper and lower planar
members ancl are respectively attached at a first end
30,32 to the semi-cylindrical wall portion 18,20. The
.; .
7~5~
--4--
support arms 26,28 also respectively have a second end
34,36 and a laterally-offset bore 38,40 projecting
through each of the spaced planar members and being
positioned intermediately oE the respective first and
second ends.
The clamp assembly 12 includes a first means
44 for moving the frame members 14,16 between a Eirst
position at which the frame members are spaced apart,
as shown in Fig. 1l and a second position at which the
frame members are adjacently disposed with respect to
one another, as shown in Fig. 2. The means 44 for
moving the frame members is attached to the second ends
34,36 of the support arms 26j28 and includes a pair of
links 46,48 respectively pivotally connected at one end
to the second links 34,36 and at an opposite end to one
another and to a rod end 50 of a fluid actuated
cylinder 52 by a pin 54.
The fluid operated cylinder 52, typically an
air cylinder, is mounted onto the end of a controllably
movable arm 56 such as the movable arm of a robot, not
shown. The movable arm 56 includes a pair of spaced
mounting brackets 58,60 having aligned bores extending
through each of the brackets for receiving a pin 62.
The pin 62 also extends through the bores 38,40 of the
support arms 26,28 pivotally interconnecting the
support arms at a position intermediate of the
respective first ends 30,32 and the second ends 34,36.
The clamp assembly 12 also includes a first
gripping member 64 attached to the first frame member
14 and a second gripping member 66 attached to the
second frame member 16. The gripping members 64,66
respectively include a compliant article-contacting
surface 67,68 and are constructed of a partially
extensible impervious material such as neoprene
rubber. The gripping members 64,66 are attached to the
frame members 14,16 by a plurality of metallic retainer
1~77~S9
--5--
strips 69 and cap screws 70 extending serially through
:, the retainer strips 69, the gripping members 64,66, and
the peripheral flanges 23,2A. The construction
effectively clamps the compliant material of the
gripping members 64,66 to the respective frame members
14,16 forming a substantially air-tight seal about the
. peripheral flanges 23,24. A pair of pressurizable
chambers 72,74 are thus defined by the wall portions
18,20 of the frame members 14,16 and the gripping
:; lO members 64,66. The compliant, article-contacting
surfaces 67,68 of the gripping members 64,66 may have a
textured pattern to improve contact and reduce slippage
between the members 64,66 and an article 10.
A second means 76 for controllably
pressurizing the gripping members includes a pair of
ports 78,80 formed respectively in the wall portions
18,20 of the frame members 14,16, and supply lines
82,84 connected respectively at one end to the ports
- 78,80 and at a second end, not shown, to a controllable
source of pressurized fluid. Typically, the
:~ controllable source of pressurized fluid includes a
: conventional directional flow control valve and an
adjustable pressure regulator connected to an air
compressor or shop air system.
In an alternative embodiment of the present
invention, not shown, it may be desirable to have only
one of the frame members movable between the first and
second positions and the other frame member fixed with
respect to -the movable arm 56. Also, it is
: 30 contemplated that one of the gripping members 64,66 may
be pre-pressurized or otherwise filled with a fluid or
foam material, with the other one of the gripping
members 64,66 being pressurizable by the second means
76.
1~7'7~
--6--
:,;
Industrial Applicabili~
;In operation, the opposed frame members 14,16
; of the clamp assembly 12 are moved to a first position
at which the Erame members are spaced apart by
extending the rod end 50 of the fluid actuated cylinder
52. This action will cause the links 46,48 to pivot
about the pin 54 and bring the second end 34,36 of the
support arms 26,28 closer together. Since the support
; arms 26,28 are pivotally interconnected at a position
intermediate the respective first ends 30,32 and the
second ends 34,36, the arms 26,28 will pivot about the
pin 62 and the attached frame members 14,16 will be
spaced apart at a first position in response to
bringing the second ends 26,28 closer together.
15At the above-described first position, at
least one, and preferably both, of the gripping members
are unpressurized and the movable arm 56, preferably
attached to a robot, is maneuvered to position the
clamp assembly 12 about an article 10 as shown in
Fig. 1.
The fluid-actuated cylinder is then actuated
to retract the rod end 50 and, by the above-described
pivot connections, move the second ends 34,36 of the
support arms apart. The attached frame members 14,16
are moved to a second position at which the frame
members are adjacently disposed as shown in Fig. 2. In
response to moving the frame members 14,16 to the
second position, the directional control valve, not
shown, is shifted to direct a flow of pressurized air
into the chambers 72,74 and pressurize the gripping
members 64,66. Under pressure, the compliant,
article-contactlng surfaces 67,68 of the gripping
members 64,66 are substantially formed to the shape of
the article 12, and a generally uniform contact force
is distributed over a broad area of the article 10.
359
7_
After clamping, the movable arm is maneuvered
as desired, to transfer the article 10 to a new
position. As shown in Fig. 3, the article 10 may be
placed on a machine tool for subse~uent machining
operations. After transfer, the clirectional control
valve is shifted and pressure is released Erom the
chambers 72,74 of the gripping members 64,66. The rod
end 50 is again extended, and the frame members 14,16
are spaced apart in the aforementioned manner.
As may be easily recognized, the compliant
surfaces 67,68 of the gripping members 64,66 is
adaptable to receiving and conforming to a wide range
of diversly sized and shaped articles. The present
invention has been found to be particularly useful in
handling a variety of stepped shafts having four or
more different diameters at various positions on a
single shaft. It has been found that shafts having a
diameter ranging from about .01 m to .15 m (0.5 in. to
6.0 in.) and weighing in a range from about .45 kg to
40 kg (1 lb to 90 lb) could be efficiently and safely
handled by the clamp assembly of the present
invention. For the above shafts, it has been found
that pressurizing the gripping members 64,66 to a
pressure in the range of about 70 kPa to 210 kPa
(10 psi to 30 psi~ is sufficient to form the compliant
surfaces 67,68 substantially about a shaft in the above
range and provide the necessary contact force for
lifting and transferring the shaft.
Other aspects, objects and advantages of this
invention can be obtained from a study of the drawings,
the disclosure and the appended claims.
